# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

# Templates implementing some generic checks.
# ==============================================================

# Declare some exceptions. This is cumbersome, but since we shouldn't need a
# lot of them, let's stack them all here. When adding a new one, put it in the
# _declare_exceptions template, and add it to the return statement. Then
# destructure in the assignment below the function declaration.
@template
@imports(_from='__builtin__', _import='Exception')
def _declare_exceptions():
    class FatalCheckError(Exception):
        '''An exception to throw from a function decorated with @checking.
        It will result in calling die() with the given message.
        Debugging messages emitted from the decorated function will also be
        printed out.'''
    return (FatalCheckError,)

(FatalCheckError,) = _declare_exceptions()

del _declare_exceptions

# Helper to display "checking" messages
#   @checking('for foo')
#   def foo():
#       return 'foo'
# is equivalent to:
#   def foo():
#       log.info('checking for foo... ')
#       ret = foo
#       log.info(ret)
#       return ret
# This can be combined with e.g. @depends:
#   @depends(some_option)
#   @checking('for something')
#   def check(value):
#       ...
# An optional callback can be given, that will be used to format the returned
# value when displaying it.
@template
def checking(what, callback=None):
    def decorator(func):
        def wrapped(*args, **kwargs):
            log.info('checking %s... ', what)
            with log.queue_debug():
                error, ret = None, None
                try:
                    ret = func(*args, **kwargs)
                except FatalCheckError as e:
                    error = e.message
                display_ret = callback(ret) if callback else ret
                if display_ret is True:
                    log.info('yes')
                elif display_ret is False or display_ret is None:
                    log.info('no')
                else:
                    log.info(display_ret)
                if error is not None:
                    die(error)
            return ret
        return wrapped
    return decorator


# Template to check for programs in $PATH.
# - `var` is the name of the variable that will be set with `set_config` when
#   the program is found.
# - `progs` is a list (or tuple) of program names that will be searched for.
#   It can also be a reference to a @depends function that returns such a
#   list. If the list is empty and there is no input, the check is skipped.
# - `what` is a human readable description of what is being looked for. It
#   defaults to the lowercase version of `var`.
# - `input` is a string reference to an existing option or a reference to a
#   @depends function resolving to explicit input for the program check.
#   The default is to create an option for the environment variable `var`.
#   This argument allows to use a different kind of option (possibly using a
#   configure flag), or doing some pre-processing with a @depends function.
# - `allow_missing` indicates whether not finding the program is an error.
# - `paths` is a list of paths or @depends function returning a list of paths
#   that will cause the given path(s) to be searched rather than $PATH. Input
#   paths may either be individual paths or delimited by os.pathsep, to allow
#   passing $PATH (for example) as an element.
#
# The simplest form is:
#   check_prog('PROG', ('a', 'b'))
# This will look for 'a' or 'b' in $PATH, and set_config PROG to the one
# it can find. If PROG is already set from the environment or command line,
# use that value instead.
@template
@imports(_from='mozbuild.shellutil', _import='quote')
def check_prog(var, progs, what=None, input=None, allow_missing=False,
               paths=None):
    if input:
        # Wrap input with type checking and normalization.
        @depends(input)
        def input(value):
            if not value:
                return
            if isinstance(value, str):
                return (value,)
            if isinstance(value, (tuple, list)) and len(value) == 1:
                return value
            configure_error('input must resolve to a tuple or a list with a '
                            'single element, or a string')
    else:
        option(env=var, nargs=1,
               help='Path to %s' % (what or 'the %s program' % var.lower()))
        input = var
    what = what or var.lower()

    # Trick to make a @depends function out of an immediate value.
    progs = dependable(progs)
    paths = dependable(paths)

    @depends_if(input, progs, paths)
    @checking('for %s' % what, lambda x: quote(x) if x else 'not found')
    def check(value, progs, paths):
        if progs is None:
            progs = ()

        if not isinstance(progs, (tuple, list)):
            configure_error('progs must resolve to a list or tuple!')

        for prog in value or progs:
            log.debug('%s: Trying %s', var.lower(), quote(prog))
            result = find_program(prog, paths)
            if result:
                return result

        if not allow_missing or value:
            raise FatalCheckError('Cannot find %s' % what)

    @depends_if(check, progs)
    def normalized_for_config(value, progs):
        return ':' if value is None else value

    set_config(var, normalized_for_config)

    return check
